The invention is generally related to the field of pre- and inter-metal dielectric films used in integrated circuits and more specifically to porous low-k dielectric films.
As integrated circuits become more and more dense, the RC delay factor associated with the interconnect layers becomes more critical. One method for improving the RC delay factor is to reduce the capacitance between metal lines. (This include both metal lines in the same metal interconnect layer and metal lines in adjacent metal interconnect layers.) For this reason, a great deal of work has been done on developing new low dielectric constant (low-K) materials for use in pre-metal, inter-metal, and intra-metal dielectrics.
One class of materials being investigated is spin-on dielectrics. Spin-on dielectrics include such materials as hydrogen silsesquioxane (HSQ) and fluorinated silicon dioxide (FSG). Unfortunately, many spin-on dielectrics involve the use of solvents that may leave a residual contamination and pose environmental waste issues.
Another class of materials being investigated is called porous dielectrics. Porous dielectrics typically have a stiff inorganic structure with air holes to reduce the overall dielectric constant. Unfortunately, to date, these films have been friable and lack the mechanical toughness to survive the subsequent chemical mechanical planarization process now being used in many interconnect fabrication sequences.
The invention is a method for forming a porous dielectric film using a halide and an organic modifier. An organically modified dielectric network structure and solid halide-containing material is co-deposited using a chemical vapor deposition process. The solid halide-containing material is then sublimated leaving a porous dielectric.
An advantage of the invention is providing a porous low-k film that is easily fabricated and has the mechanical toughness to withstand subsequent processing.
This and other advantages will be apparent to those of ordinary skill in the art having reference to the specification in conjunction with the drawings.